I spent all day reading about gateways, routing, etc. in order to setup
Linux as my gateway.  I actually got it setup, but from what I understand
the approach I tried is terribly insecure.

I did this and got it running:
# echo 1 >/proc/sys/net/ipv4/ip_forward
# ipchains -F
# ipchains -P forward ACCEPT
# ipchains -A forward -s 192.168.1.0/24 -d 0/0 -j MASQ

That works, but everything is reset when I restart my network.  And, as I
read, this is apparently insecure.

What is the proper way to do this?

We'll use these numbers as an example of my net config:
eth0 192.168.1.1   # The LAN obviously.
eth1 24.32.5.105   # The DHCP assigned WAN IP


Thanks,
David